Recently, optical recording media, such as compact discs (CDs) and digital versatile discs (DVDs), are widely used to record large-volume digital data. In particular, optical recording media that allow users to record data thereto (recordable media) are rapidly gaining popularity, and many people now use the recordable media to easily and cost-effectively record large-volume digital data, such as image data and music data. Accompanying the popularity of such optical recording media, there is a growing demand for recording media that allow the users to print objects onto the surfaces opposite to the light-incident surfaces (hereinafter, simply referred to as the “label surface”) using printers so as to produce originally designed optical recording media. Optical recording media of this type have already been developed and have been commercially available.
These optical recording media have “ink-receiving layers” on the label surfaces to affix ink. Printing on the label surface is conducted by applying ink on the ink-receiving layers using inkjet printers.
In general, the print quality is lower on the optical recording media than on glossy paper. Thus, although inkjet printers have the ability to product high-quality prints, such an ability has not been fully applied to the optical recording media. To overcome this problem, Japanese Unexamined Patent Application Publication No. 2002-237103 provides an optical recording medium comprising an ink-receiving layer having a surface roughness limited to a predetermined value or lower.
In order to reduce the surface roughness of the ink-receiving layer, the ink-receiving layer is preferably formed by spin coating. In such a case, the surface roughness of the ink-receiving layer is affected by the underlying layer. Consequently, even when a coating solution capable of forming a flat, smooth surface is selected, the surface roughness of the resulting ink-receiving layer is not necessarily small, and high print quality is not necessarily achieved.
As is apparent from the above, decreasing the surface roughness of the ink-receiving layer prepared by spin coating has not been easy.
Furthermore, Japanese Unexamined Patent Application Publication No. 9-288847 discloses a DVD-type optical recording medium having a colored supporting substrate (sometimes referred to as a “dummy substrate”).